This invention relates to new and useful improvements in mobile wheelchair lifts and in particular, automatic fail safe braking systems therefore.
The present device is designed specifically to raise a person in a wheelchair from the platform level up to a rail car level and vice versa although of course it may be used in other environments.
The alternative to this present device is to install powered lifts attached directly to the rail cars, but this has been abandoned by the railways as prohibitively expensive and impractical.
However, both manually operated and power driven types of wheelchair lifts are known and the following prior art is exemplary.
U.S. Pat. No. 3291260 issued Dec. 13, 1966 to D.F. Woor et al. This discloses a vehicle lift apparatus including a pulley system and safety mechanisms which prevent downward movement of the platform if the supporting cable becomes slack.
U.S. Pat. No. 3435915 issued Apr. 1, 1969 to J. Villars shows a lifting installation including a fail safe arrangement which is operative if a cable becomes slack or fractures.
U.S. Pat. No. 4133437 issued Jan. 9, 1979 to F. Alan Gates shows a device in which the platform is mounted on a rotatable post in front of a doorway in the side of a van and is operated electrically. This has a belt and pulley drive with the belt being frictionally restrained to prevent inadvertent or unwanted lowering.
U.S. Pat. No. 4347030 issued Aug. 31, 1982 to John C. Kingston shows a loading and detraining apparatus with a horizontal loading platform which is pivotally connected to a pair of spaced apart and opposed linkage means. This is a stationary apparatus and is particularly suited for lifting wheelchairs over stairwells in the vestibule of a train coach. It utilizes a balk lever for raising the platform.
U.S. Pat. No. 4493602 issued Jan. 15, 1985 to Charles F. Koerber. This discloses a lift apparatus of rotary construction which includes a brake system for the lift assembly and automatically lifts the wheelchair user from the ground into the van and vice versa. It includes a fail safe braking system.
U.S. Pat. No. 4499970 issued Feb. 19, 1985 to Ian G. Hussey. This shows a lifting platform for a transit system and utilizes a set of rotating actuating arms to raise and lower the platform. It utilizes a chain drive and sprocket wheel combination.
U.S. Pat. No. 4576539 issued Mar. 18, 1986 to Harold R. Williams. This is a curb side lift apparatus for transferring wheelchair passengers to and from trains and public transit vehicles. This is a stationery device utilizing a chain and sprocket arrangement for raising and lowering the platform.
The present device includes several significant features which include the fact that it is extremely light and easy to handle because of the extensive use of aluminum in the construction thereof.
Secondly, it is easily portable due to the fact that when the platform is in the lowermost position, the frame is raised and the ground engaging wheels under the platform enable it to be moved from one location to another readily and easily.
It is designed primarily for use with a manual cranking system which is extremely efficient and includes a braking system that is activated by the load on the wheelchair deck so that the manual effort required to crank the lift downwardly is proportional to the load on the deck.
The required high degree of safety and reliability in the braking and holding system is obtained by providing two band brakes in connection with a spring loaded retracting crank thus giving two safety methods to prevent inadvertent descent of the loading platform during use.
Another advantage of the invention is the automatic compensation for wear occurring between the brake bands and brake drums and the fact that the efficiency of the brakes can be adjusted readily and easily.
In accordance with the invention there is provided a mobile wheelchair lift comprising in combination a base frame, a vertically situated support structure extending upwardly from adjacent each end of said base frame, a substantially horizontal wheelchair platform, a winch assembly including a cable drum and a cable system operatively connected thereto, and supporting said platform between said support structure for elevating and lowering action within said support structure, said cable system including at least one upper pulley, upper pulley support means and a cable operatively extending between said cable drum and said upper pulley, and an automatic braking system cooperating between said winch assembly and said platform to prevent inadvertent descent of such platform, said braking system including at least one brake drum means operatively connected to said cable drum, brake means operatively connected to said brake drum means, and operating link means operatively extending between said upper pulley support means and said brake means to actuate said brake means, said upper pulley support means including a cam action therein for pivotally supporting same to said vertical support structure whereby the initiation of descent of said platform moves said link means to actuate said brake means.
In accordance with a further advantage of the invention, there is provided an automatic braking system for mobile wheelchair lifts in which said wheelchair lift includes a base frame, vertically situated support structure extending upwardly from at least each end of said base frame and a substantially horizontal wheelchair plateform mounted within said support structure, a winch assembly including a cable drum, and a cable system within said support structure and operatively connected to said platform for selective elevating and lowering said platform within said support structure, said cable drum rotating in one direction when said platform is elevating and in the opposite direction when said platform is descending; said braking system including automatically operating means to prevent inadvertent descent of said platform, said automatically operating means including brake drum means and brake means operatively connected to said brake drum means both operatively associated with said cable drum, one way clutch means to engage said brake drum means and said cable drum when said cable drum starts to rotate in said opposite direction, an upper pulley system for said cable system, pulley support means for said upper pulley systems situated adjacent the upper end of said vertically situated support structure, operating a link means operatively extending between said upper pulley support means and said brake means to actuate said brake means, said upper pulley support means including a cam action therein for pivotally supporting same to said vertical support structure whereby the initiation of descent of said platform moves said operating link means to actuate said brake means.
A still further advantage of the invention is to provide a device of the character herewithin described which is simple in construction, economical in manufacture and otherwise well suited to the purpose of which it is designed.
With the foregoing in view, and other advantages as will become apparent to those skilled in the art to which this invention relates as this specification proceeds, the invention is herein described by reference to the accompanying drawings forming a part hereof, which includes a description of the best mode known to the applicant and of the preferred typical embodiment of the principles of the present invention, in which: